Rijndael is adopted as Advanced Encryption Standard (AES) by thernAmericanâ€™s National Institute of Standards and Technology sincern2001. AES algorithm has a wide area of application for its goodrnsecurity, simple design and ease of implementation on hardware andrnsoftware. A Monte Carlo Test (MCT) vector is released with AESrnalgorithm submission to check correctness of implementations.rnBesides to its defined purpose, MCT is used to measure speed ofrnexecution.rnVery important information flows through conventionalrncommunication systems like telephone, fax and radio. In suchrnsystems, cryptographic solutions can be implemented using embeddedrnsystems. ARM is the most common embedded system processor. Thernchallenge is to run cryptography algorithms that are computationallyrnintensive in nature on an embedded platform with an inherent resourcernlimitation.rnIn this thesis, AES implementation is optimized for speed of executionrnon an ARM powered embedded platform. It starts by comparison ofrnavailable approaches to implement for a better speed performance.rnThen, Key features of the ARM processor are studied and exploited onrnthe implementation to enhance speed of execution of the algorithm.rnThe encryption has shown a remarkable improvement than therndecryption. This is because of the design complexity on AESrndecryption algorithm. For the communication flow control problemrnthat might be caused by the speed imbalance of encryption andrndecryption, a counter mode of operation is recommended.